Abbaye de Saint-Gildas-des-Bois, Romanesque Benedictine abbey in Saint-Gildas-des-Bois, France.

Abbaye de Saint-Gildas-des-Bois is a Benedictine monastery built around the 12th century from reddish sandstone and shaped by Romanesque architectural style. The structure displays typical features of the period with thick walls, rounded arches, and a simple yet solid appearance.

Felix, abbot of Saint-Gildas de Rhuys, urged Simon I de La Roche-Bernard to allow a new Benedictine abbey on his Lampridic estate. In 1026 eight monks left Redon under Helogon, the first abbot; the two men brought Gildas's relics from Rhuys. Commendation imposed in 1492 began a decline, and the abbey was suppressed in 1790.

The name comes from the relics of Saint Gildas, which arrived in the Middle Ages and drew pilgrims from across the region seeking healing and spiritual comfort. This connection to the saint shaped how people viewed and used this place for centuries.

The abbey church stands in the centre of Saint-Gildas-des-Bois, in the Loire-Atlantique department of the Pays de la Loire. The church has been a classified monument historique since 30 December 1994, while the other abbey buildings were inscribed on 2 July 2003. Visitors approach on foot through the village; the nave, transept and choir of the late 12th century are the parts to look for.

The abbey church preserves the relics' pull: pilgrims came especially on three pardon days, 29 January (Gildas's death), 11 May (his body's return to Rhuys) and 1 July (the relics' arrival at Lampridic). The reliquary itself disappeared in the early years of the French Revolution.